The present invention is concerned with an exposure delay mechanism for a photographic camera, more specifically with an exposure delay mechanism for a single lens reflex camera, and with single lens reflex cameras modified by the incorporation therein of an exposure delay mechanism.
As is well known in the art, single lens reflex cameras include a reflex mirror which is mounted within the camera body and movable between two positions, usually by a spring biasing mechanism. In one position, the mirror reflects the image gathered by the lens system through a prism for viewing by the photographer. This may be referred to as the view-finding position. While in this position, the mirror is interposed between the lens system and the film to be exposed. Therefore, when it is desired to operate the camera to expose the film, the camera operating mechanism necessarily provides for moving the reflex mirror out of its view-finding position into a film exposing position in which it is removed from the light path between the lens system and the film. In most single lens reflex camera such movement of the reflex mirror is part of a continuous sequence of camera operation to expose the film. In such sequence, the mirror is rapidly moved with a snap-type action to the film exposing position, usually coming abruptly to rest against a stop and the shutter is automatically opened immediately as the mirror clears the optical path between the lens and the film. One result is that the mechanical vibration induced by the movement and abrupt stop of the mirror persists while the film is being exposed. As discussed below, the prior art has provided means to minimize such vibration. In ordinary photography such vibration does not significantly affect the quality of the photographs obtained particularly when shock absorbers or similar devices known to the art are employed. However, when employing such cameras for microscopic or astronomical photography, such vibration causes significant blurring of the photographic images obtained.
The prior art has attempted to deal with this problem. Some cameras, for example a Nikon F camera, are provided with a manual mirror release mechanism so that, after the photographer sights the image to be photographed in the view finder, he can manually move the mirror from the view finding to the film exposing position. Then, after so long an interval as desired, he operates the shutter to expose the film. Although this enables the photographer to wait any desired interval to allow the vibrations caused by the mirror movement to settle down, this system has the significant disadvantage that the manual force required to move the camera has a tendency, particularly troublesome in astronomical work, to cause slight shifting of the camera with resultant loss of the exact field of viewing sighted by the photographer while the mirror was in its view finding position. Further, this method leaves the photographer "blind" between exposures, i.e. once the mirror is moved to the film exposing position the photographer is unable to use the view finder unless the mirror is manually returned to the view finding position. Manual back and forth operation of the mirror tends to move the camera out of position. Although such cameras can be modified at considerable expense to provide for a push button type mechanism to move the mirror from, and return it to, the view finding position, the necessity for touching the camera body and imposing a sufficient force thereon to operate the pushbutton still produces undesirable shifting of the camera and vibrations.
Other cameras are known, for example, the Miranda Laborec, which have a mechanism built into the camera body which enables the photographer to raise the mirror and pause for as long as desired before tripping the shutter. This operation may be controlled by means of a remote operating cable such as an air bulb cable release. This camera, while well suited for astronomical photography is not well suited for general photography. Thus, the general photographer, if interested in astronomical or microscopic photography, much purchase a second camera specifically designed for it.
A number of prior patents deal with problems associated with vibration due to movement of the reflex mirror. For example, U.S. Pat. No. 3,860,941 discloses a shock absorbing device employed in a single lens reflex camera to attenuate vibrations caused by movement of the mirror. U.S. Pat. No. 3,003,066 discloses a mechanism providing a two-step raising of the mirror in order to reduce the shock of the movement and sudden stop of the mirror. U.S. Pat. No. 3,882,523 discloses a mirror operating mechanism in which, in order to reduce shock, the drive which operates to move the mirror to its upper position is locked against further operation when the mirror is held in its upper position. U.S. Pat. No. 3,653,311 discloses a coil type shock absorber mechanism to attenuate the shock of reflex mirror movement and sudden stopping. Other patents which illustrate other aspects of the mechanism of single lens reflex cameras are U.S. Pat. Nos. 2,952,196 and 3,062,118.
U.S. Pat. No. 2,210,610 deals with a direct viewing type of camera which utilizes a branched remote control cable means to simultaneously expose the image being photographed and identifying serial number.
It is accordingly an object of the present invention to provide a novel exposure delaying mechanism adapted to inexpensively and simply modify a single lens reflex camera to permit delay of shutter operation and thereby exposure of the film for any selected interval after the normal exposure sequence of the camera has progressed sufficiently to move the mirror into its film exposing position. This permits the operator to delay for any desired interval, including an interval long enough to permit all vibrations due to movement of the mirror to dissipate the time between mirror movement and film exposure.
It is another object of the invention to provide a novel exposure delay mechanism which may be operated remotely by means of remote operating or air bulb devices without the necessity for physically touching the camera body or an operating switch directly affixed thereto.
It is yet another object of the present invention to provide an inexpensive and simple device for modifying a single lens reflex camera by interrupting the normal camera operating sequence at a point after movement of the reflex mirror is completed and before operation of the shutter as commenced.
It is another object of the present invention to provide an improved single lens reflex camera having an exposure delay mechanism adapted particularly for telescopic and microscopic photography.